USB to Serial adapter issues

[turbo_bu]

Just upgraded laptops and have finally had to deal with the dreaded USB to serial adapter woes. I know Paul has said get a real serial port (found on another post about getting a cable to work (http://forum.efilive.com/showthread.php?14492-DIY-cable-problems&highlight=USB+to+serial+adapter)

"Most USB-Serial adapters are not capable of generating the correct baud rate required for ALDL communications. The baud rate required in 8192 baud. A Real PC UART chip controlling a real RS232 serial port is capable of generating a baud rate of 8228 which is close enough to 8192 to allow it to work. I recommend using a real serial port, you may need to get your desktop computer (if it has a serial port) close to your vehicle to test whether the cable works using a real serial port. If it does then you can be pretty confident that the Serial-USB converter is not generating the correct baud rate.

Regards
Paul "

But right now, that just isn't an option for me any more (my old laptop was 8+ years old :) ).

Anyway, found a Prolific USB to serial adapter, and performing the TTS test, shows that the speed is off .... like 12.7% off (7151 instead of 8192 baud). And yes, this is the same cable, same car, same PCM that everything worked with before. Thus, I am pretty positive it is the USB adapter (already verified COM settings and ports were setup correctly).

This brings me to my question of which USB adapter have people had better luck with? I hate to have to keep trying / returning until I find one that works with my laptop.

I did see someone mention that they were having luck with megasquirts using this PCMCIA to serial adapter:
http://www.newegg.com/Product/Product.aspx?Item=N82E16839328020

Is it blind hope that the PCMCIA type design is better than the USB ones???

[Blacky]

Is it blind hope that the PCMCIA type design is better than the USB ones???

No its not blind hope. What you're looking for is a PCMCIA card that contains a real UART* chip (most of them do) rather than firmware emulation like what is found on most USB-serial adapters. A real UART chip allows the EFILive software to reprogram the baud rate to within 0.5% of 8192 which is close enough to work.

I guess if you could find a USB-serial adapter that claims to have a real physcial UART chip (or a perfect software emulation of one) then that might work also. But I've never heard of one :(

*UART=Universal Asynchronous Receiver Transmitter.

Regards
Paul

[kangsta]

try an adapter that uses a FTDI chip. I have used a few different ones with ALDL and worked perfectly, you need the VCP drivers (Virtual Com Port)

[turbo_bu]

Paul,

Thanks for the reply. I tried to look at the SYBA one, (one listed on the newegg link), but it doesn't say if it has it's own UART or not.

"Support up to two RS232 serial ports Compliant with 32-bit Cardbus PC Card Type II standard Hot Plug and Plug-&-Play compatibility Compatible with industrial standard 16C550 UART Automated hardware / software flow control available Supports serial data transfer rate of up to 1Mbps Supports 5-, 6-. 8-bit data framing Supports 1 or 2 Stop bit operation 16-byte receive and transmit FIFO to reduce CPU overhead"

Do you know of any other PCMCIA to serial adapters that have a real UART or not?

kangsta,

Do you happen to know of any name brands to look for that use the FTDI chip? At this point, I would just like to limit my trips to the store guessing and checking :)

[Blacky]

with industrial standard 16C550 UART Automated hardware

I'd say that part of the quote says that it will work, but I can't say for sure, its still a lottery.

P.S. If Kangsta's had success with a particular device I'd try that first - at least you know its been tested and found to work.

Regards
Paul

[kangsta]

Unfortunately mine were all custom jobs on a PCB with the max232 etc for ALDL. Look for a converter with a FTDI FT232 chip. Try ebay for FTDI.

[kangsta]

N.B. Max232 is a RS232 to TTL converter. You can also get USB to TTL converter with a FTDI chip which may be simpler than USB to RS232 to TTL setup...

[turbo_bu]

kangsta -

Going straight to TTL would be very nice.

Would something like this work? (just did a quick USB to TTL search).

http://www.amazon.com/USB-3-3v-TTL-DB9-Adapter/dp/B004LC5RMO

A couple of quick questions though - would one of these be able to talk at the desired 8192 baud? Does it have to be 5 volts or is 3.3 volts enough?

Thanks for all the help

[turbo_bu]

Maybe Paul or someone else might be able to help clarify ....

Did some more reading about TTL, RS232, the Max232 chip etc... (disclaimer, mechanical engineer ... not electrical engineer ... so I could be wrong on some of this stuff :) )

RS232 kicks out a + or - voltage signal (roughly 3 to 15 volts) to represent the 0's and 1's.
The car wants a TTL voltage signal (0 or 5 volts) to reprsent the 0's and 1's.
The ALDL cables typically have a Max232 chip with some other capacitors, resistors, power supply etc... to do the conversion.

There are some USB to TTL devices out there that would elimate the need for an ALDL cable. Big question I guess is now has anyone ever tried using this on an OBDI car??? How well does the USB to TTL adapter produce the desired 8192 baud rate?? From what I have played with, getting the baud rate correct is THE MOST IMPORTANT part of getting the laptop to talk to the PCM.

BTW - another adapter that I saw while surfing around:
http://www.ebay.com/itm/USB2-0-to-TTL-UART-Convertor-/270852429771?pt=BI_Electrical_Equipment_Tools&hash=item3f101017cb

Features:

•High Speed USB2.0 Compatible
•TTL UART Output 5V/3.3V IO tolerance
•Full modem signal with hardware flow control
•Integrated 1024-Byte EEPROM for vendor ID, product
ID
•Baud rates: 300 bps to 1 Mbits
•576 Byte receive buffer; 640 byte transmit buffer
•Onbard 3.3V regulator, output 5V & 3.3V supply for external circuit
•All signals marked on silkscreen
•Three different USB plug type provide and please choose only one after payment (default is type A USB plug)

It says TTL UART ... and the tech sheet shows a UART on the board (see PDF file). wonder if you can set the rate to say 8200 like Paul said and that should be close enough?

update: did a quick look at the specks (see additional PDF file) it appears that 9600 is all you get (either that or 7200).

Guess the next question is how / why did the ol' laptops serial port get 8192 (or 8200 which ever the case may be) to work in the first place????

[kangsta]

kangsta -

Going straight to TTL would be very nice.

Would something like this work? (just did a quick USB to TTL search).

http://www.amazon.com/USB-3-3v-TTL-DB9-Adapter/dp/B004LC5RMO

A couple of quick questions though - would one of these be able to talk at the desired 8192 baud? Does it have to be 5 volts or is 3.3 volts enough?

Thanks for all the help

It uses a FTDI chip so it may work, only part I'm not sure about is the 5V/3.3V part. It's been a while since I looked at the specs in detail.

[Blacky]

update: did a quick look at the specks (see additional PDF file) it appears that 9600 is all you get (either that or 7200).

Guess the next question is how / why did the ol' laptops serial port get 8192 (or 8200 which ever the case may be) to work in the first place????

That is exactly the problem that USB-Serial convertors have, they usually only support a preset number of "common" baud rates. The UART chip in a PC (or in a PCMCIA card) is software configurable (that's what the "universal" means). Because its configurable, the PC software can configure it to support almost any baud rate.

Regards
Paul

[turbo_bu]

Paul,

Thanks for the further details.

Is there some other "description" of a UART that I should be looking for? At this point, it doesn't appear as though many adapters list too many spec's in their descriptions. Guess it will still come down to some trial and error.

[powertrippin]

http://www.saelig.com/USAC/U004.htm
this works great its a ftdi
and cheap under 20
Ed